A $40\mathrm{.}4-$g sample of solid silver nitrate is mixed in a beaker with $60\mathrm{.}6g$ of water to give $68\mathrm{.}5mL$ of a colorless transparent liquid.

$($a$)$ What is the density of this liquid? $\frac{g}{m}L$

$($b$)$ Is this liquid a pure substance, a homogeneous mixture or a heterogeneous mixture?

$($c$)$ When an equal volume of the molecular liquid octane is added to the beaker, two layers are seen to form. The contents of the beaker are now a

$($d$)$ If the density of liquid octane is $0\mathrm{.}703\frac{g}{m}L,$ is octane the layer on the top in the beaker or the layer on the bottom?